1. Field of the Invention
The present invention relates to an expanded programmable machine controller connected to a main body programmable machine controller (PMC) inside a numerical control apparatus, and more specifically, to an expanded programmable machine controller which can independently carry out a debugging, operations and the like while not connected to the main body PMC.
2. Description of the Related Art
A numerical control apparatus contains a programmable controller (PC) for controlling the mechanical units or devices of a machine tool, and the PC contained in the numerical control apparatus is referred to as a programmable machine controller (PMC).
When a machine tool is complex, and units such as a pallet changer and the like are added to, for example, a machining center, the PMC in the numerical control apparatus must contain a sequence program and the like having a larger capacity and be able to carry out a processing at a higher speed to control these units.
Further, when these mechanical units are selected as necessary, to constitute the machining center or the like, and the type of the units is increased, the pallet changer, for example, must be able to select the number of pallets required, and to satisfy such a requirement, it is necessary to modify the sequence program or the number of the I/O circuits and the like of the PMC contained in the numerical control apparatus.
Nevertheless, it is very time-consuming to create or modify a sequence program for each arrangement of machine tools, and further, the development, debugging and the like of the sequence programs also take a very long time.
To cope with this requirement, an expanded PMC (programmable machine controller) is employed and used for each mechanical unit to be controlled. The expanded PMC is disposed outside of a numerical control apparatus and controls only, for example, a mechanical unit such as a pallet changer and the like, and thus a machine tool not provided with a pallet changer need not include the expanded PMC. Note, in contrast to the expanded PMC, a PMC disposed inside of a numerical control apparatus is referred to as a main body PMC. Japanese Patent Application No. Hei 1-23505 filed by the applicant discloses an example of such an expanded PMC.
Nevertheless, when the main body PMC is connected to the expanded PMC to form an entire system, conventionally the debugging of a system program for operating the system cannot be carried out unless the entire system has been completed. Therefore, to carry out the debugging of the expanded PMC, the main body PMC is also needed, and further, the debugging of the sequence program of the main body PMC must have been completed. If, however, the sequence program of the expanded PMC and the sequence program of the main body PMC can be independently developed, during the development of an actual machine tool, the period needed for developing a program can be shortened. Conversely, sometimes there is a need to debug the sequence program of a main body PMC after the sequence program of an expanded PMC has been completed. In general, a preferable developing process is that whereby the sequence program of a main body PMC serving as a central PMC is debugged after the respective units have been debugged.